Method and Apparatus for Feeding Back and Receiving Acknowledgement Information of Semi-Persistent Scheduling Data Packets

ABSTRACT

The application relates to radio communications and discloses a method and apparatus for feeding back and receiving acknowledgment (ACK) information of semi-persistent scheduling (SPS) data packets. The method includes receiving downlink data packets and an uplink data assignment indicator (UL DAI) from a base station, wherein a value of the UL DAI indicates a number (N) of all scheduled downlink sub-frames which scheduled by the base station for the user equipment, the number N is greater than 1, and a number k (k&lt;N) of the downlink data packets is/are semi-persistent scheduling (SPS) data packets; forming a feedback signal comprising N acknowledgements/negative acknowledgements (ACKs/NAKs) acknowledging the N downlink data packets, k ACKs/NAKs of the k SPS data packets is/are placed from (N−k+1)th to Nth positions of the N ACKs/NAKs; and sending the feedback signal to the base station starting from the ACK/NAK at the first position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/720,915, now U.S. Pat. No. 8,565,182, filed on Dec. 19, 2012. TheU.S. patent application Ser. No. 13/720,915 is a continuation of U.S.patent application Ser. No. 13/094,697, now U.S. Pat. No. 8,358,621,filed on Apr. 26, 2011. The U.S. patent application Ser. No. 13/094,697is a continuation of U.S. patent application Ser. No. 12/610,618, nowU.S. Pat. No. 8,249,010, filed on Nov. 2, 2009. The U.S. patentapplication Ser. No. 12/610,618 is a continuation of InternationalApplication No. PCT/CN2009/071486, filed on Apr. 27, 2009. TheInternational Application No. PCT/CN2009/071486 claims priority toChinese Patent Application No. 200810217254.3, filed on Nov. 5, 2008.All of the afore-mentioned patent applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The disclosure relates to radio communications, and in particular, to amethod and apparatus for feeding back and receiving acknowledgementinformation of semi-persistent scheduling data packets.

BACKGROUND

Two modes are supported in the 3GPP E-UTRA (Third Generation PartnershipProject-Evolved Universal Terrestrial Radio Access) system: a frequencydivision duplexing (FDD) mode and a time division duplexing (TDD) mode.In the TDD mode, the length of each radio frame is 10 milliseconds (ms)and the radio frame is composed by two 5 ms length half-frames. Eachhalf-frame is composed by eight 0.5 ms timeslots and three specialfields, namely, a downlink pilot timeslot (DwPTS), a guard period (GP)and an uplink pilot timeslot (UpPTS). Two timeslots form a sub-frame,and the DwPTS, GP, and UpPTS form a special sub-frame. The length of thesub-frame is 1 ms.

Currently, two modes are available for feeding back an acknowledgementor negative acknowledgement (ACK/NAK) of multiple downlink sub-frames inan uplink sub-frame in the 3GPP E-UTRA system: multiplexing mode andbundling mode. In the multiplexing mode, if a feedback occurs in aphysical uplink control channel (PUCCH), the feedback is related to anuplink-downlink configuration; if the feedback occurs in a physicaldownlink shared channel (PDSCH), the number of bits fed back depends onwhether an uplink grant (UL Grant) signaling exists. If the UL Grantsignaling exists, the number of bits that a user equipment (UE) isrequired to feed back is specified through an uplink data assignmentindicator (UL DAI) field in the signaling. For example, if a basestation (BS) schedules x of the total N downlink sub-frames, the UEfeeds back x ACKs/NAKs; if no UL Grant signaling exists, the UE feedsback N bits and a NAK to those non-scheduled downlink sub-frames.

In the bundling mode, only 1-bit ACK/NAK information is fed back, in thePUCCH or in the PUSCH, to indicate the details of all the scheduleddownlink sub-frames. So long as the feedback to a scheduled downlinksub-frame is a NAK, the final feedback is a NAK. The final feedback isan ACK only when feedbacks to all the scheduled downlink sub-frames areACKs.

Two data scheduling modes are defined in the current Long Term Evolution(LTE) protocol: dynamic scheduling mode and semi-persistent scheduling(SPS) mode, i.e. two types of resource indicators of data transmission.In the dynamic scheduling mode, each new data packet has a controlsignaling—physical downlink control channel (PDCCH) to indicateresources and transmission mode. The UE receives downlink data andtransmits uplink data according to the PDCCH delivered by the basestation (BS). In the SPS mode, the BS sends a PDCCH control signalingonly when the SPS transmission is activated. The UE activates the SPStransmission according to the position and time indicated by the PDCCH.The UE transmits and receives new data packets in a certain period untilanother PDCCH in a special format terminates the SPS transmission.

Because the PDCCH is used for notification in both dynamic schedulingand semi-persistent scheduling modes, the UE differentiates whether thescheduling mode is dynamic scheduling or semi-persistent scheduling bydifferent scrambled IDs in a cyclic redundancy check (CRC) of the PDCCH.In the dynamic scheduling mode, the CRC of the PDCCH is scrambled with acell radio network temporary identifier (C-RNTI); in the semi-persistentscheduling mode, the CRC of the PDCCH is scrambled with asemi-persistent scheduling cell radio network temporary identifier(SPS-C-RNTI). When the UE detects the PDCCH scrambled with theSPS-C-RNTI, the UE activates the semi-persistent transmission, andreceives or transmits data according to the indication in the PDCCH.Within the subsequent period of time, the UE receives and transmits dataonly according to the position indicated by the PDCCH when thesemi-persistent transmission is activated for the first time, making itunnecessary to notify the UE of the position of SPS data packetresources through the PDCCH each time. When the position of SPSresources needs to be changed, a new PDCCH may be used to replace theprevious semi-persistent scheduling configuration until thesemi-persistent transmission is cancelled by a PDCCH scrambled with anSPS-C-RNTI in a special format when the period of SPS data expires.

However, in uplink ACK/NAK multiplexing mode in the prior art, the firstposition of K ACKs/NAKs fed back by the UE is the ACK/NAK of the SPSsub-frame, and the position of the UL ACK/NAK of other sub-frames isarranged in the sequence of downlink data assignment indicator (DL DAI).If the UE does not detect any data in the sub-frames, the UE feeds backa NAK. When the UE loses the SPS activation signaling, the UE feeds backa NAK at the first position. Based on the NAK, the BS thinks that thecontrol signaling is received properly but data is wrong, thus receivingincorrect ACK information. As a result, the BS does not retransmit aPDCCH, and the UE still does not know the position of thesemi-persistent transmission, which causes unnecessary retransmission.

SUMMARY OF THE INVENTION

One objective of embodiments of the present invention is to provide amethod and apparatus for feeding back ACK information of SPS datapackets so that the ACK information of downlink data can be fed backproperly.

Another objective of embodiments of the present invention is to providea method and apparatus for receiving ACK information of SPS data packetsso that the ACK information of downlink data can be received properly.

To achieve the preceding objectives, embodiments of the presentinvention provide the following technical solutions. A method forfeeding back ACK information of SPS data packets includes: receivingdownlink data and an uplink data assignment indicator (UL DAI) from abase station (BS), where a value of the UL DAI indicates a number (N) ofdownlink data packets; placing ACKs/NAKs of k SPS data packets of thedownlink data packets at positions from a (N−k+1)^(th) ACK/NAK to aN^(th) ACK/NAK; and feeding back N ACKs/NAKs to the BS.

A method for receiving ACK information of SPS data packets includes:sending downlink data and an uplink data assignment indicator (UL DAI)to a user equipment (UE), where a value of the UL DAI indicates a number(N) of downlink data packets; and receiving N ACKs/NAKs fed back sentfrom the UE, among which positions from a (N−k+1)^(th) ACK/NAK to aN^(th) ACK/NAK is/are used for placing k SPS data packets of thedownlink data packets.

An apparatus for feeding back ACK information of SPS data packetsincludes: a receiving unit configured to receive downlink data and anuplink data assignment indicator (UL DAI) from a base station (BS),wherein a value of the UL DAI indicates a number (N) of downlink datapackets; a processing unit configured to place ACKs/NAKs of k SPS datapackets of the downlink data packets at positions from a (N−k+1)^(th)ACK/NAK to a N^(th) ACK/NAK; and a feedback unit configured to feed backN ACKs/NAKs to the BS.

An apparatus for receiving ACK information of SPS data packets includes:a sending unit configured to send downlink data and an uplink dataassignment indicator (UL DAI) to a user equipment (UE), wherein a valueof the UL DAI indicates a number (N) of downlink data packets; and areceiving unit configured to receive N ACKs/NAKs fed back by the UE,among which positions from a (N−k+1)^(th) ACK/NAK to a N^(th) ACK/NAKis/are used for placing k SPS data packets of the downlink data packets.

Compared with the prior art, embodiments of the present invention havethe following differences and benefits. The ACKs/NAKs of k SPS datapackets of the downlink data packets are placed to positions from the(N−k+1)^(th) ACK/NAK to the N^(th) ACK/NAK. In this case, when the SPSactivation PDCCH signaling or the override PDCCH signaling of the SPSsub-frames is missing, the UE cannot differentiate whether thesub-frames are dynamic scheduling sub-frames or SPS sub-frames. If theACKs/NAKs of the SPS data packets of the downlink data packets areplaced at the N^(th) ACK/NAK for feedback, N ACKs/NAKs can be arrangedcorrectly. Furthermore, when the BS receives the ACK information of NACKs/NAKs that are arranged correctly, unnecessary data retransmissionsmay be reduced, thus saving resources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method for feeding back ACK information ofSPS data packets according to an embodiment of the present invention;

FIG. 2 is a flowchart of a method for receiving ACK information of SPSdata packets according to an embodiment of the present invention;

FIG. 3 is a schematic drawing illustrating the receiving of SPSsub-frames in a method for receiving ACK information of SPS data packetsaccording to another embodiment of the present invention;

FIG. 4 is a schematic drawing illustrating the receiving of SPSsub-frames in a method for receiving ACK information of SPS data packetsaccording to another embodiment of the present invention;

FIG. 5 is a schematic drawing illustrating the receiving of SPSsub-frames in a method for receiving ACK information of SPS data packetsaccording to another embodiment of the present invention;

FIG. 6 is a schematic drawing illustrating the receiving of SPSsub-frames in a method for receiving ACK information of SPS data packetsaccording to another embodiment of the present invention;

FIG. 7 shows a structure of an apparatus for feeding back ACKinformation of SPS data packets according to an embodiment of thepresent invention; and

FIG. 8 shows a structure of an apparatus for receiving ACK informationof SPS data packets according to an embodiment of the present invention.

DETAILED DESCRIPTION

For better understanding of the objectives, technical solutions andmerits of the present invention, the following describes the presentinvention in detail with reference to the accompanying drawings andexemplary embodiments.

FIG. 1 is a flowchart of a method for feeding back ACK information ofSPS data packets according to an embodiment of the present invention. Asshown in FIG. 1, the method includes the following steps.

Step 101: Receive downlink data and an uplink data assignment indicator(UL DAI) from a base station (BS), where a value of the UL DAI indicatesa number (N) of the downlink data packets.

Step 102: Place ACKs/NAKs of k semi-persistent scheduling data packetsof the downlink data packets at positions from a (N−k+1)^(th) ACK/NAK toa N^(th) ACK/NAK, where k is a positive integer greater than 0.

Step 103: Feed back N ACKs/NAKs to the base station.

The placing the ACKs/NAKs of the k semi-persistent scheduling datapackets of the downlink data at the positions from the (N−k+1)^(th)ACK/NAK to the N^(th) ACK/NAK of step 102 includes: placing theACKs/NAKs of the k semi-persistent scheduling data packets of thedownlink data at the positions from the (N−k+1)^(th) ACK/NAK to theN^(th) ACK/NAK in positive or negative sequence.

Step 102 further includes: placing ACKs/NAKs of non-semi-persistentscheduling data packets of the downlink data at positions from a firstACK/NAK among the N ACKs/NAKs. Specifically, the step includes:receiving a downlink data assignment indicator (DL DAI) from the basestation, where a value of the DL DAI indicates that a downlink datapacket is an M^(th) non-semi-persistent scheduling data packet of thedownlink data packets; and placing a ACK/NAK of the M^(th)non-semi-persistent scheduling data packet at position of a M^(th)ACK/NAK.

In this embodiment, the ACKs/NAKs of the k semi-persistent schedulingdata packets of the downlink data are placed to the positions from the(N−k+1)^(th) ACK/NAK to the Nth ACK/NAK. In this case, when thesemi-persistent scheduling activation PDCCH signaling or the overridePDCCH signaling of the semi-persistent scheduling sub-frames is missing,the UE cannot differentiate whether the sub-frames are dynamicscheduling sub-frames or semi-persistent scheduling sub-frames. If theACKs/NAKs of the k semi-persistent scheduling data packets of thedownlink data are placed at the positions from the (N−k+1)^(th) ACK/NAKto the Nth ACK/NAK, the N ACKs/NAKs can be arranged correctly.

FIG. 2 is a flowchart of a method for receiving ACK information of SPSdata packets in an embodiment of the present invention. As shown in FIG.2, the method includes the following steps.

Step 201: Send downlink data and an uplink data assignment indicator (ULDAI) to a user equipment (UE), where a value of the UL DAI indicates anumber (N) of the downlink data packets.

Step 202: Receive N ACKs/NAKs fed back by the UE, among which positionsfrom a (N−k+1)^(th) ACK/NAK to a N^(th) ACK/NAK are used for placing ksemi-persistent scheduling data packets of the downlink data packets.

When the base station receives a feedback i.e. NAK, responding to thesemi-persistent scheduling activation sub-frame, another semi-persistentscheduling activation signaling is transmitted at a next time ofsemi-persistent transmission or at time of semi-persistent schedulingretransmission. The transmitted signaling is the same as or differentfrom the semi-persistent scheduling activation signaling.

The step of placing the ACKs/NAKs of the non-SPS data packets of thedownlink data packets to the positions from the first ACK/NAK among theN ACKs/NAKs in step 202 includes sending a downlink data assignmentindicator (DL DAI) to the UE, where a value of the DL DAI indicates thatthe downlink data packet is a M^(th) non-SPS data packet of the downlinkdata packets, and receiving M ACKs/NAKs from the UE, among which theACK/NAK of the M^(th) non-SPS data packet is placed at the position of aM^(th) ACK/NAK.

The ACKs/NAKs of k SPS data packets of the downlink data packets areplaced to the positions from the (N−k+1)^(th) ACK/NAK to the N^(th)ACK/NAK. In this case, when the SPS activation PDCCH signaling or theoverride PDCCH signaling of the SPS sub-frames is missing, the UE cannotdifferentiate whether the sub-frames are dynamic scheduling sub-framesor SPS sub-frames. If the ACKs/NAKs of k SPS data packets of thedownlink data packets are placed to positions from the (N−k+1)^(th)ACK/NAK to the N^(th) ACK/NAK, the N ACKs/NAKs can be arrangedcorrectly. Thus, when the BS receives the N ACKs/NAKs that are arrangedcorrectly, unnecessary data retransmissions may be reduced, thus savingresources. The preceding embodiment is based on the TDD mode. The TDDmode has the following features: Sub-frames 0 and 5 must be downlinksub-frames; sub-frame 2 must be an uplink sub-frame; the DwPTS maytransmit downlink data or not transmit data; the rest of sub-frames maybe assigned as uplink or downlink sub-frames flexibly.

TABLE 1 Assignment ratio of uplink sub-frames to downlink sub-frames inthe TDD system Uplink-downlink sub-frames Sub-Frame No. Assignment ratio0 1 2 3 4 5 6 7 8 9 3:1 (5 ms) D S U U U D S U U U 2:2 (5 ms) D S U U DD S U U D 1:3 (5 ms) D S U D D D S U D D 3:6 (10 ms) D S U U U D D D D D2:7 (10 ms) D S U U D D D D D D 1:8 (10 ms) D S U D D D D D D D 5:3 (10ms) D S U U U D S U U D

As shown in Table 1, seven uplink-to-downlink assignment ratios aredefined in the 3GPP E-UTRA system, including three assignment ratios forthe period of 5 ms, namely, 1:3, 2:2 and 3:1, and four assignment ratiosfor the period of 10 ms, namely, 6:3, 7:2, 8:1 and 3:5. Except theassignment ratios of 1:3 and 3:5, the assignment ratios may cause thefollowing result: ACKs/NAKs of N (greater than 1) downlink sub-framesneed to be fed back in an uplink sub-frame.

Taking the assignment ratio of 2:2 as an example, when the DwPTStransmits downlink data, the ACK/NAK feedbacks to the downlinksub-frames should be assigned to the downlink sub-frames evenly. Thus,one of two uplink sub-frames must feedback ACKs/NAKs of two downlinksub-frames. These N downlink sub-frames may be dynamic schedulingsub-frames or SPS sub-frames. The BS may schedule one or multipledownlink sub-frames of N downlink sub-frames. For example, it mayschedule only one downlink sub-frame or all of the N downlinksub-frames, which is determined by the scheduler of the BS according toservices. The dynamic scheduling is random scheduling, in which only onedownlink sub-frame can be scheduled once. The BS may dynamicallyschedule any downlink sub-frame. A PDCCH is required in the dynamicscheduling of each downlink sub-frame. The SPS is a mode in whichmultiple downlink sub-frames are scheduled by period. Except that aPDCCH is required in the SPS of the first downlink sub-frame, no PDCCHis required in the subsequent SPS of downlink sub-frames.

The 3GPP LTE technology defines a series of requirements to avoid HARQinteraction errors. The requirements are as follows.

1. A 2-bit UL DAI is used in the UL Grant to indicate the number ofscheduled PDSCH sub-frames of the UE. The PDSCH sub-frames includedynamic sub-frames and SPS sub-frames. In certain cases, for example, todetermine the number of SPS sub-frames, the value of the UL DAI mayinclude the number of non-SPS sub-frames only. In these cases, the UEobtains the number (N) of PDSCH sub-frames by counting the sum of thenumber of SPS sub-frames and the number of non-SPS sub-frames indicatedby the UL DAI, where N indicates the number of uplink ACKs/NAKs that theUE needs to feed back.

2. A 2-bit DL DAI is used in the DL Grant to indicate the current numberof PDSCH sub-frames assigned to the UE. In ACK/NAK multiplexing mode,the DL DAI counts only the number of PDSCH sub-frames assigned to the UEuntil the current time by using a counter, without counting the numberof SPS sub-frames. The SPS sub-frames may be sub-frames that carrydownlink SPS data without resource scheduling index signaling orsub-frames that carry downlink SPS data and SPS override PDCCH. The SPSsub-frames may also be sub-frames that carry downlink SPS data andinclude sub-frames carrying the SPS activation signaling PDCCH andsub-frames of the SPS override PDCCH.

3. In uplink ACK/NAK multiplexing mode, the first position among NACKs/NAKs fed back by the UE is the ACK/NAK of the SPS sub-frame. The ULACKs/NAKs of other sub-frames are arranged according to the sequence ofthe DL DAI.

4. If the UE does not detect any data in the sub-frames, the UE feedsback a NAK.

In uplink ACK/NAK multiplexing mode in the prior art, the first positionof N ACKs/NAKs that the UE feeds back according to the UL DAI is theACK/NAK of the SPS sub-frame. The ACKs/NAKs of other sub-frames arearranged according to the sequence of the DL DAI. If the UE does notdetect any data in the sub-frames, the UE feeds back a NAK. Thus, whenthe SPS activation PDCCH is missing, errors may occur in UL ACK/NAKmultiplexing feedback because the UE cannot differentiate whether thesub-frame is a dynamic sub-frame or an SPS sub-frame.

FIG. 3 is a schematic drawing illustrating the receiving of SPSsub-frames in a method for receiving ACK information of SPS data packetsin another embodiment of the present invention. As shown in FIG. 3, theSPS transmission is activated by the downlink resource assignment (DLGrant) signaling. The frequency resources indicated by the DL Grantcarry semi-persistent transmission data packets. If the UE does notreceive the DL Grant signaling, it should feedback DTX, which means nodata is received, but the UE actually feeds back a NAK. The BS does notdetermine whether the NAK indicates the UE does not receive the DL Grantsignaling or whether it indicates the UE receives the DL Grant signalingbut errors occurred during the detection of SPS data packets. If the BSbelieves that the NAK indicates that the UE receives the DL Grantsignaling, it thinks that the SPS resources are already activated, andsends new SPS data packets after a certain period. Because the DL Grantis unavailable in SPS mode, the UE cannot obtain correct SPS data withina certain period. As shown in Table 1, supposing when the BS retransmitsSPS data packets, the assignment ratio of uplink sub-frames to downlinksub-frames is 1:3, the first sub-frame carries semi-persistent datapackets and the second and third sub-frames are dynamic schedulingsub-frames. Based on prior art, the values of the DL DAIs in the DLGrants of the second and third sub-frames should be 0 and 1, and thevalue of the DAI in the UL Grant of the uplink sub-frame is 3. When theUE receives the four downlink sub-frames, supposing the second sub-frameis received correctly, the third sub-frame is also received correctly.When the UE sends feedback in the uplink, it does not think that thefirst sub-frame is an SPS sub-frame because the DAI of the UL Grant is3, the DL DAI of the DL Grant of the received second sub-frame is 0, andthe UE does not receive PDCCH of the SPS activation frame. This iscaused by the requirement in the prior art that the ACK/NAK of the SPSsub-frame must be fixed at the first position of the multiplexing group.Thus, the UE feeds back an ACK, an ACK and a NAK, but the BS expects theUE to feed back a NAK, an ACK, and an ACK. This is caused by thedifference between judgments of the BS and the UE about whether thefirst sub-frame is an SPS sub-frame. Further, the UE does not receivethe SPS activation signaling, but the BS thinks that the UE receives theSPS activation signaling. As a result, the UE feeds back a NAKresponding to the SPS data packets within the SPS duration, and the BSdoes not retransmit the PDCCH. Thus, the UE does not know the positionof the semi-persistent transmission, which causes unnecessaryretransmissions.

This embodiment provides an improved solution for overcoming theweaknesses of the prior art, in which when the BS retransmits SPS datapackets, the assignment ratio of uplink sub-frames to downlinksub-frames is 1:3; and feedback errors occur when the ACKs/NAKs of theSPS sub-frames must be fixed at the first position of the multiplexinggroup (N ACKs/NAKs). The improved solution is as follows. When the ULACK/NAK multiplexing is performed on the uplink ACK/NAK associated withthe SPS downlink sub-frame, the uplink ACK/NAK is fixed at the lastposition in the multiplexing group (N ACKs/NAKs) for transmission.

If the DwPTS can also carry downlink data, four downlink sub-frames andone uplink sub-frame are available within 5 ms. If three downlinksub-frames are scheduled for one user equipment, the first one of thesethree downlink sub-frames is an SPS sub-frame and the second and thirddownlink sub-frames carry downlink dynamic scheduling data. In thiscase, the UL DAI may count the total number of scheduled downlinksub-frames of the user equipment. A value of the UL DAI is equal to 3.Because the first downlink sub-frame is the SPS sub-frame, the number ofthe SPS subframes does not be counted in to the DL DAI parameter. Thesecond downlink sub-frame is the dynamic scheduling data, a value of theDL DAI is equal to 0. The third downlink sub-frame is also a dynamicscheduling data sub-frame, a value of the DL DAI is equal to 1. If theUE loses the semi-persistent transmission data packet (downlinksub-frame 1) and activation DL Grant of the semi-persistent transmissionbut receives dynamic scheduling data of other sub-frames, the UE cannotknow that the first downlink sub-frame is an SPS sub-frame. The UEdetermines that three UL ACKs/NAKs need to be fed back based on the factthat the UL DAI is equal to 3. Because the DL DAI of the second downlinksub-frame is equal to 0, the UE may misunderstand that the seconddownlink sub-frame is a first downlink sub-frame scheduled by the BS,and then feedback an ACK at a first position in the multiplexing group(i.e. N ACKs/NAKs). According to the fact that the DL DAI is equal to 1at the third downlink sub-frame, the UE determines that the thirddownlink sub-frame is a second scheduled downlink sub-frame, and feedsback an ACK at the second position in the multiplexing group (i.e. NACKs/NAKs). Because no data is detected at a fourth downlink sub-frame,the UE may determine that the fourth downlink sub-frame is the thirdscheduled sub-frame which is not received, and then feedback a NAK atthe third position in the multiplexing group. Thus, the UE feeds back anACK, an ACK, and a NAK. According to this embodiment, when the ULACK/NAK multiplexing is performed on the uplink ACK/NAK associated withthe SPS downlink sub-frame, the uplink ACK/NAK of the semi-persistentscheduling downlink sub-frames is fixed at the last position in themultiplexing group for transmission. That is, the UE places theACKs/NAKs of the SPS sub-frame at the third position among the threeACKs/NAKs. Thus, the BS should receive the feedbacks ACK, ACK, and NAK.In this case, the sequence of ACKs/NAKs that the UE sends is the same asthat of ACKs/NAKs that the BS should receive.

In addition, in this embodiment, if the BS receives a feedback of a NAKresponding to the semi-persistent scheduling activation sub-frame, theBS transmits another PDCCH which is same as a semi-persistent schedulingactivation PDCCH in a next period of semi-persistent data transmission,or retransmits a PDCCH which is same as a semi-persistent schedulingactivation PDCCH at a position for semi-persistent scheduling sub-frameretransmission. The UE transmits or receives semi-persistent schedulingdata according to resources indicated by the PDCCH, and activates thesemi-persistent scheduling transmission.

This embodiment places the ACK/NAK of semi-persistent scheduling datapacket of the downlink data at the position of the third ACK/NAK forfeedback. Thus, when the semi-persistent scheduling activation PDCCHsignaling is missing, the UE cannot differentiate whether the sub-framesare dynamic scheduling sub-frames or semi-persistent schedulingsub-frames. If the ACK/NAK of the semi-persistent scheduling data packetof the downlink data is placed at the position of the third ACK/NAK forfeedback, the three ACKs/NAKs can be arranged correctly. In addition,this embodiment takes only the assignment ratio of the uplink sub-frames1:3 as an example. Other six assignment ratios are also applicable tothe present invention, and will not be further described.

Furthermore, when the SPS transmission is normally activated, a new DLGrant may be used to replace the previous semi-persistent schedulingconfiguration when the period of SPS data expires. When a sub-frame ofthe override PDCCH is counted into the DL DAI and the ACK/NAK associatedwith the SPS sub-frame needs to be placed at the first position in theACK/NAK multiplexing group, errors may occur if the PDCCH of thesub-frame is missing.

FIG. 4 is a schematic drawing illustrating the receiving ofsemi-persistent scheduling sub-frames in a method for receivingacknowledgement information of semi-persistent scheduling data packetsin another embodiment of the present invention. As shown in FIG. 4, theBS schedules three downlink sub-frames in a case of the assignment ratioof the uplink sub-frames to the downlink sub-frames is equal to 1:3. Inthis case, the value of UL DAI is equal to 3. Sub-frame A is an SPSoverride sub-frame. Thus, the value of DL DAI of the SPS overridesub-frame is equal to 0. Sub-frames C and D are dynamic schedulingsub-frames, and their value of DL DAIs are respectively equal to 1 and2. When the SPS override PDCCH occurs at the sub-frame A, only sub-frameC can be received if the PDCCHs of sub-frame A and D are missing. Inthis case, the UE knows that the value of the UL DAI of sub-frame C isequal to 3 and the value of the DL DAI of sub-frame C is equal to 1.However, the UE does not know that sub-frame A is an SPS overridesub-frame. Instead, the UE thinks that sub-frame A is still an SPSsub-frame that is not counted in the DL DAI. Thus, the UE maymisunderstand that sub-frame B is used as the sub-frame of which the DLDAI is equal to 0. As a result, when the ACK/NAK associated with the SPSsub-frame is fixed at the first position in the multiplexing group, theUE feeds back a NAK, a NAK and an ACK, but the BS should receive thefeedbacks NAK, ACK and NAK. As result, the feedbacks of the UE actuallysends is different from that of the BS should receive.

This embodiment provides an improved solution for overcoming theweaknesses of the prior art, in which the ACK/NAK of the SPS sub-framesare fixed at the first position in the multiplexing group for feedback;and feedback errors occur when the override PDDCH signaling of thesemi-persistent scheduling sub-frames is missing. The improved solutionis as follows: When the assignment ratio of the uplink sub-frames to thedownlink sub-frames is 1:3, four downlink sub-frames and one uplinksub-frame are available within the period of 5 ms if the DwPTS can carrydownlink data. When the UL ACK/NAK multiplexing is performed on theuplink ACKs/NAKs associated with the SPS downlink sub-frames, the uplinkACK/NAK is fixed at the last position in N ACKs/NAKs for transmission;that is, the ACK/NAK is fixed at the third position. In this case, theBS should receive the feedbacks NAK, ACK and NAK. According to the factthat the DL DAI and UL DAI of sub-frame C are respectively equal to 1and 3, the UE may misunderstand that sub-frame B is a dynamic schedulingsub-frame and feed back a NAK responding to sub-frame B, and thatsub-frame A is an SPS sub-frame and feed back a NAK responding tosub-frame A at the last position in the UL ACK/NAK multiplexing group.The UL ACKs/NAKs of other sub-frames are arranged according to thesequence of the DL DAI. The UE actually feeds back a NAK, an ACK and aNAK. In this case, the sequence of feedbacks that the UE actually sendsis the same as that of feedbacks that the BS should receive.

This embodiment places the ACK/NAK of semi-persistent scheduling datapacket of the downlink data at the position of the third ACK/NAK forfeedback. Thus, when the override PDCCH signaling of the semi-persistentscheduling sub-frames is missing, the UE cannot differentiate whetherthe sub-frames are dynamic scheduling sub-frames or semi-persistentscheduling sub-frames. If the ACK/NAK of the SPS data packet of thedownlink data is placed at the position of the third ACK/NAK forfeedback, the sequence of feedbacks that the UE actually sends is thesame as that of feedbacks that the BS should receive. In addition, thisembodiment takes only the assignment ratio of the uplink sub-frames isequal to 1:3 as an example. Other six assignment ratios are alsoapplicable to the present invention, and will not be further described.

The embodiment shown in FIG. 3 is based on the fact that the SPSactivation PDCCH of an SPS sub-frame is missing. However, the number oftransmitted SPS sub-frames is not limited to 1 in this embodiment. Thisembodiment supposes there are two SPS sub-frames, among which the SPSactivation PDCCH of one SPS sub-frame is missing, and the other SPSsub-frame is transmitted normally. FIG. 5 is a schematic drawingillustrating the receiving of SPS sub-frames in a method for receivingACK information of SPS data packets in another embodiment of the presentinvention. As shown in FIG. 5, sub-frame B is the SPS sub-frame of whichthe SPS activation PDCCH is missing and sub-frame C is the SPS sub-framethat is normally transmitted without DL Grant. Errors may occur if theACK/NAK of the SPS data packet of the downlink data is placed at theposition of the first ACK/NAK for feedback. The specific analysis is asfollows. The BS schedules three downlink sub-frames for the UE, andvalue of the UL DAI is equal to 3. Sub-frame A carries dynamicscheduling data. In this case, value of the DL DAI is equal to 0, andthe UE receives the sub-frame and feeds back an ACK, that is, an ACK isfed back because of DL DAI=0. The UE does not receive PDCCH of the SPSactivation sub-frame at the position of sub-frame B. Thus, the UE doesnot think that sub-frame B is an SPS sub-frame, but misunderstands thatsub-frame B is a dynamic scheduling sub-frame. As a result, the UE feedsback a NAK at the third position. Sub-frame C is an SPS sub-frame thatis normally transmitted without DL Grant. The UE receives the sub-frameC and should feedback an ACK at the first position. In fact, the UEfeeds back an ACK, an ACK and a NAK. The BS should receive the feedbacksNAK, ACK and ACK. In this case, the sequence of feedbacks that the UEactually sends is different from that of feedbacks that the BS shouldreceive.

To solve this problem, this embodiment arranges the ACKs/NAKs associatedwith the SPS sub-frames behind the dynamic sub-frames in a certainsequence when the UL ACK/NAK multiplexing is performed on the uplinkACKs/NAKs associated with the SPS downlink sub-frames. According to thisembodiment, value of the DL DAI of sub-frame A is equal to 0, andsub-frame A is a dynamic scheduling sub-frame which an ACK should be fedback, where the ACK should be placed at the position of the firstACK/NAK. Sub-frame B is an SPS sub-frame to which a NAK should be fedback; sub-frame C is an SPS sub-frame to which an ACK should be fed backat the position of the third ACK/NAK. The positions of ACKs/NAKs of theSPS sub-frames are arranged according to the arrival sequence ofsub-frames B and C. The BS should receive the feedbacks ACK, NAK andACK. According to the fact that values of the DL DAI and UL DAI ofsub-frame A are respectively equal to 0 and 3, the UE may determine thatsub-frame A is a dynamic scheduling sub-frame and feed back an ACK atthe first position because value of the DL DAI is equal to 0. Becausethe PDCCH of sub-frame B is missing, the UE may misunderstand thatsub-frame B is a dynamic scheduling sub-frame, and feed back a NAK atthe second position of the UL ACK/NAK. Sub-frame C is an SPS sub-frameand is received correctly. In this case, an ACK is placed at the lastposition. In fact, the UE feeds back an ACK, a NAK and an ACK. In thiscase, the sequence of feedbacks that the UE actually sends is the sameas that of feedbacks that the BS should receive.

This embodiment places respectively the ACKs/NAKs of two SPS datapackets of the downlink data at the positions of the second and thirdACKs/NAKs for feedback. Thus, when the SPS activation PDCCH signaling ismissing, the UE cannot differentiate whether the sub-frames are dynamicscheduling sub-frames or SPS sub-frames. If the ACKs/NAKs of the SPSdata packets of the downlink data are placed respectively at thepositions of the second and third ACKs/NAKs for feedback, the threeACKs/NAKs can be arranged correctly. In addition, this embodiment takesonly two SPS data packets as an example. More than two SPS data packetsmay also be applicable to the present invention. This embodiment isbased on the condition that the SPS activation PDCCH signaling ismissing. The following conditions are also applicable to the presentinvention: The SPS activation PDCCH signaling is missing and the normalSPS data packet is missing, which will not be further described.Furthermore, this embodiment takes only the assignment ratio of theuplink sub-frames is equal to 1:3 as an example. The other sixassignment ratios are also applicable to the present invention, and willnot be further described.

The preceding embodiments are based on the condition that the BSschedules three downlink sub-frames for the UE. The method for receivingACK information of SPS data packets in another embodiment of the presentinvention is based on the following conditions: The assignment ratio ofuplink sub-frames to downlink sub-frames is 1:3; four downlinksub-frames are available within the period of 5 ms; the BS schedulesfour downlink sub-frames for the UE; and when the semi-persistenttransmission begins, the transmission of SPS sub-frame data packetsfails and the PDCCHs of dynamic sub-frames are missing. FIG. 6 is aschematic drawing illustrating the receiving of SPS sub-frames in amethod for receiving ACK information of SPS data packets in anotherembodiment of the present invention. As shown in FIG. 6, if the DwPTScan carry downlink data, four downlink sub-frames and one uplinksub-frame are available within the period of 5 ms. When thesemi-persistent transmission begins, the UE receives semi-persistenttransmission data sub-frames at a fixed time within a certain period ifthe transmission of SPS sub-frame A fails and the PDCCH of dynamicsub-frame B is missing. When the UL ACK/NAK multiplexing is performed onthe uplink ACKs/NAKs associated with the SPS downlink sub-frames, theuplink ACK/NAK is fixed at the last position in the multiplexing groupfor transmission. The UE knows that sub-frame A is an SPS sub-frame anddetects that sub-frame A data is missing. Then, the UE feeds back a NAK.The UE does not detect any PDCCH in sub-frame B. The UE detects data insub-frame C, and deduces that sub-frame B loses a dynamic datascheduling sub-frame according to the fact that the value of the DL DAIis equal to 1. The UE detects that sub-frame D is correct and has afeedback ACK. Because the value of the UL DAI is equal to 4, the UEneeds to feed back four ACKs/NAKs. According to the arrangement sequenceof the DL DAI and the method for placing SPS sub-frames at the lastposition, the UE gives feedbacks as follows: NAK, ACK, ACK, and NAK.Further, the BS should receive the feedbacks NAK, ACK, ACK and NAK.Thus, the sequence of feedbacks that the UE actually sends is the sameas that of feedbacks that the BS should receive.

FIG. 7 shows a structure of an apparatus for feeding back ACKinformation of SPS data packets in an embodiment of the presentinvention. As shown in FIG. 7, the feedback apparatus 10 includes: areceiving unit 11 configured to receive downlink data and an uplink dataassignment indicator (UL DAI) from a base station (BS), where a value ofthe UL DAI indicates a number (N) of the downlink data packets; aprocessing unit 12 configured to place the ACKs/NAKs of k SPS datapackets of the downlink data packets at positions from a (N−k+1)^(th)ACK/NAK to a N^(th) ACK/NAK; and a feedback unit 13 configured to feedback N ACKs/NAKs to the BS. The processing unit 12 is further configuredto place ACKs/NAKs of non-SPS data packets of the downlink data packetsat positions from a first ACK/NAK among the N ACKs/NAKs. The processincludes receiving a downlink data assignment indicator (DL DAI) fromthe BS, where a value of the DL DAI indicates that the downlink datapacket is an M^(th) non-SPS downlink data packet; and placing theACK/NAK of the M^(th) non-SPS data packet at a position of an M^(th)ACK/NAK.

In addition, the processing unit 12 may place the ACKs/NAKs of the k SPSdata packets of the downlink data packets at the positions from the(N−k+1)^(th) ACK/NAK to the Nth ACK/NAK in positive or negativesequence. The details are given in the third to sixth embodiments of thepresent invention, and will not be further provided.

This embodiment places the ACKs/NAKs of the k SPS data packets of thedownlink data at the positions from the (N−k+1)^(th) ACK/NAK to theN^(th) ACK/NAK. In this case, when the SPS activation PDCCH signaling orthe override PDCCH signaling of the SPS sub-frames is missing, the UEcannot differentiate whether the sub-frames are dynamic schedulingsub-frames or SPS sub-frames. If the ACKs/NAKs of k SPS data packets ofthe downlink data are placed to positions from the (N−k+1)^(th) ACK/NAKto the N^(th) ACK/NAK, N ACKs/NAKs can be arranged correctly.

FIG. 8 shows a structure of an apparatus for receiving ACK informationof SPS data packets in an embodiment of the present invention. As shownin FIG. 8, the receiving apparatus 20 includes: a sending unit 21configured to send downlink data and an uplink data assignment indicator(UL DAI) to a user equipment (UE), where a value of the UL DAI indicatesa number (N) of the downlink data packets; and a receiving unit 22configured to receive N ACKs/NAKs fed back by the UE, among whichpositions from a (N−k+1)^(th) ACK/NAK to a N^(th) ACK/NAK are used forplacing k SPS data packets of the downlink data packets. When thereceiving unit 22 receives a feedback NAK to an SPS activationsub-frame, the sending unit 21 is further configured to transmit anotherSPS activation signaling at a next time of semi-persistent transmission,or transmit another SPS activation signaling at time of SPSretransmission, where the retransmitted signaling is the same as ordifferent from the SPS activation signaling. In addition, the ACKs/NAKsof the non-SPS data packets of the downlink data packets are placed atpositions from a first position of the N ACKs/NAKs in the receiving unit22. The process includes sending a downlink data assignment indicator(DL DAI) to the UE, where a value of DL DAI indicates that the downlinkdata packet is a M^(th) non-SPS downlink data packet; and receiving MACKs/NAKs fed back by the UE, among which the M^(th) non-SPS data packetis placed at the position of a M^(th) ACK/NAK. The details are given inthe preceding method embodiments.

Embodiments of the present invention place the ACKs/NAKs of k SPS datapackets of the downlink data packets to positions from the (N−k+1)^(th)ACK/NAK to the N^(th) ACK/NAK. In this case, when the SPS activationPDCCH signaling or the override PDCCH signaling of the SPS sub-frames ismissing, the UE cannot differentiate whether the sub-frames are dynamicscheduling sub-frames or SPS sub-frames. If the ACKs/NAKs of the k SPSdata packets of the downlink data packets are placed at the positionsfrom the (N−k+1)^(th) ACK/NAK to the N^(th) ACK/NAK, N ACKs/NAKs can bearranged correctly. Thus, when the BS receives ACK information of the NACKs/NAKs that are arranged correctly, unnecessary data retransmissionsmay be reduced, thus saving resources.

Through the preceding description of embodiments, it is understandableto those skilled in the art that embodiments of the present inventionmay be implemented by hardware or software in combination with anecessary hardware platform. Thus, the technical solution of the presentinvention may be made into software. The software may be stored in anon-volatile storage medium (for example, a CD-ROM, a USB flash disk,and a mobile hard disk), and include several instructions that enable acomputer device (PC, server, or network device) to perform the methodsprovided in each embodiment of the present invention.

Although the present invention has been described through some exemplaryembodiments and accompanying drawings, the invention is not limited tosuch embodiments. It is apparent that those skilled in the art can makevarious modifications and variations to the invention without departingfrom the spirit and scope of the invention.

1. A method for a user equipment to feedback acknowledgement informationof semi-persistent scheduling (SPS) data packets, comprising: obtaininga quantity N of physical downlink shared channel (PDSCH) sub-frames thatare scheduled by a base station for the user equipment, the scheduledPDSCH sub-frames including at least one SPS sub-frame and at least onedynamic scheduling sub-frame; forming a feedback signal comprising Nacknowledgements/negative acknowledgements (ACKs/NAKs) in response tothe N PDSCH sub-frames scheduled for the user equipment, wherein thefeedback signal comprises at least one ACK/NAK in response to the atleast one SPS sub-frame and at least one ACK/NAK in response to the atleast one dynamic scheduling sub-frame, and wherein the at least oneACK/NAK in response to the at least one SPS sub-frame is/are placedbehind the at least one ACK/NAK in response to the at least one dynamicscheduling sub-frame; and sending the feedback signal to the basestation.
 2. The method according to claim 1, wherein an SPS sub-frame isa sub-frame that carries a data packet without a resource schedulingindex, and a dynamic scheduling sub-frame is a sub-frame that carries adata packet with a resource scheduling index.
 3. The method according toclaim 1, wherein the scheduled PDSCH sub-frames include one SPSsub-frame, and the ACK/NAK in response to the SPS sub-frame is placed inthe feedback signal at the last position of the N ACKs/NAKs.
 4. Themethod according to claim 1, wherein the obtaining the quantity N ofPDSCH sub-frames that are scheduled by the base station for the userequipment comprises: receiving an uplink data assignment indicator (ULDAI) and the N PDSCH sub-frames from the base station, wherein the ULDAI indicates the quantity N of the scheduled PDSCH sub-frames.
 5. Auser equipment, comprising: a receiver, configured to obtain a quantityN of physical downlink shared channel (PDSCH) sub-frames that arescheduled by a base station for the user equipment, the scheduled PDSCHsub-frames including at least one semi-persistent scheduling (SPS)sub-frame and at least one dynamic scheduling sub-frame; a processor,configured to form a feedback signal comprising Nacknowledgements/negative acknowledgements (ACKs/NAKs) in response tothe N PDSCH sub-frames scheduled for the user equipment, wherein thefeedback signal comprises at least one ACK/NAK in response to the atleast one SPS sub-frame and at least one ACK/NAK in response to the atleast one dynamic scheduling sub-frame, and wherein the at least oneACK/NAK in response to the at least one SPS sub-frame is/are placedbehind the ACK/NAK in response to the at least one dynamic schedulingsub-frame; and a transmitter, configured to send the feedback signal tothe base station.
 6. The user equipment according to claim 5, wherein anSPS sub-frame is a sub-frame that carries a data packet without aresource scheduling index, and a dynamic scheduling sub-frame is asub-frame that carries a data packet with a resource scheduling index.7. The user equipment according to claim 5, wherein the scheduled PDSCHsub-frames include one SPS sub-frame, and the ACK/NAK in response to theSPS sub-frame is placed in the feedback signal at the last position ofthe N ACKs/NAKs.
 8. The user equipment according to claim 5, wherein thereceiver is configured to receive an uplink data assignment indicator(UL DAI) and the N PDSCH sub-frames from the base station, wherein theUL DAI indicates the quantity N of the scheduled PDSCH sub-frames. 9-18.(canceled)
 19. A computer program product comprising a non-transitorystorage medium having stored thereon a computer program for use by auser equipment, wherein the program comprises: instructions forobtaining a quantity N of physical downlink shared channel (PDSCH)sub-frames that are scheduled by a base station for the user equipment,the scheduled PDSCH sub-frames including at least one semi-persistentscheduling (SPS) sub-frame and at least one dynamic schedulingsub-frame; instructions for forming a feedback signal comprising Nacknowledgements/negative acknowledgements (ACKs/NAKs) in response tothe N PDSCH sub-frames scheduled for the user equipment, wherein thefeedback signal comprises at least one ACK/NAK in response to the atleast one SPS sub-frame and at least one ACK/NAK in response to the atleast one dynamic scheduling sub-frame, and wherein the at least oneACK/NAK in response to the at least one SPS sub-frame is/are placedbehind the ACK/NAK in response to the at least one dynamic schedulingsub-frame; and instructions for sending the feedback signal to the basestation.
 20. The computer program product according to claim 19, whereinthe scheduled PDSCH sub-frames include one SPS sub-frame, and theACK/NAK in response to the SPS sub-frame is placed in the feedbacksignal at the last position of the N ACKs/NAKs. 21-22. (canceled)